Process of refining hydrocarbon liquids under high vacuum



NOV. 17, 1931. w, W GRlMM 1,832,202 PROCESS 0F REFINING HYDROCARBON LIQUIDS UNDER HIGH VACUUM Filed June 25,' 1926 2 Sheets-Shea! l www Nov. 17, 1931. W. w. GRIMM l,832,202

PROCESS OF REFINING HYDROCARBON LIQUIDS UNDER HIGH VACUUM Patented Nov. i7, 1931 WARREN W. GRIMM, OIE NACOGDOCHES, TES

PROCESS OF REFINING HYDROCARBON LIQUIDS UNDER HIGH VACUUM Application led June 25, 1926. Serial No. 118,427.

distillate containing the desirable lubricating'oils,.which distillate may be fractionally condensed to complete the extraction of the oils from the petroleum. Generally, the lubricating stock of crude petroleum comprises oils of intermediate boiling points and, in accordance with the practice of the invention,

the complex distillate is made up of these intermediate boiling point oils and toward the end of the process they are fractionally condensed according to their boiling points, thus producing lubricating oils of different grades. Normally, it is impossible to heat petroleum to a suficiently high temperature to evolve such a complex mixture Without encountering cracking to an undesirable degree, or some other form of objectionable decomposition and, accordingly, the invention contemplates the employment of a high vacuum in connection with temperatures below those of objectionable decomposition. By means of placing the heated petroleum under vacuum, lower temperatures can be relied upon to produce the desired distillation.

Inasmuch as the presence within many grades of petroleum of lower boiling point oils will interfere with the establishment of the vacuum preferred by the invention, it is contemplated tonremove such oils from the petroleum before the latter is admitted to the vacuum-stage of the process. Thus, by heating the petroleum and submitting it to distillation at atmospheric, or substantially atmospheric, pressure, the lower boiling point oils will vaporize toform a distillate which may be condensed to effect extraction from the crude petroleum of the lower boiling point oils. It will be appreciated that the extent to which the petroleum is topped or skimmed of its lower boiling point constituents willdepend upon the temperature to grades.

which it is heated in advance of the atmospheric distillation stage.

Once the lower boiling point oils have been removed, the petroleum is, in accordance with the invention, thereafter submitted to the action of a single, substantially uniform, high vacuum to evolve a complex distillate containing the desired lubricating oils. Thus,

"the petroleum, having left the atmospheric distillation stage, is subjected to a high vacu-l t um, lwhereupon intermediate boiling point oils of the desired type are instantly and simultaneously vaporized to produce a complex distillate. There remains from the vacuum distillation a residue containing the very highest boiling point constituents, such, for example, as tarry and impure matters, and these are immediately conducted away from the vacuum distillation stage. Thus, the

tarry and impure matters are immediately re- 70 evolved during the vacuum distillation are 75- fractionally condensed in some suitable manner to produce lubricatin oils of different Of course, it will be appreciated that the extent to which the intermediate boiling point oils will be vaporized in the 80 vacuum distillation stage depends upon two i factors, namely, the temperature of the petroleum entering the vacuum distillation zone and the magnitude of the vacuum maintained, and that either of these may be varied .85

pheric distillation stage, and that the heat 100 supplied is subsequently employed to obtain additional distillation under vacuum.

Further objects and features of the invention will become apparent from a reading of the following description, in the light of the accompanying drawings. It must, however, be understood that the accompanying drawings are .of a conventional or diagrammatic character and in the nature of a flow sheet, which disclses arrangements of apparatus adapted for the practice of the invented process, and that the invention is not limited to the form of apparatus illustrated. I Fig. 1 is a diagrammatcal view of a system for carrying out the process, and

Fig. 2 is a vertical sectional view of the partial condensers.

In the drawings the numeral 10 designates a pump through which the hydrocarbon liquid is introduced and conveyed by a pipe l1 to a heat exchanger 12 of suitable structure, which may be provided with a heating furnace 12 if desired, as shown in Fig. 1.

A pipe 13 conducts the preheated liquid to a retort, which is illustrated in the form of a pipe still 14, of suitable construction, and is equipped with a coil 15, through which the liquid passes. The liquid is charged in a continuous fio and heated to a desired degree in the still 14 and is conducted from the pipe coil 15 by pipe 16, through pipe 162 to a separator 17 in which it is continuously ejected from a spray head 18 and partly vaporized at atmospheric pressure or substantially atmospheric pressure. Light fractions are thus vaporized and pass over baffle means 22', effecting separation of heavier fractions, into vapor line 23 and condenser 36 wherein vapors of such light fractions are condensed and such condensates collected in tank 42.

lAfter the lighter fractions have thus been removed the remaining liquid is conducted from the separator 17 through pipe 163 into a chamber 17 v in which it is continuously ejected from a spray head 18 and the remainingvolatile ingredients vaporized under high vacuum into a complex mixture of vapors. The. chamber 17 is maintained` at such temperature as will permit separation of tarry and impure matters, which will settle to the bottom of the chamber or separator, and will be conducted continuously by reflux pipe 19 to the heat exchanger. Here the heat of the residue will be transferred to the liquid being charged to still `14:, and the residue finally removed by pump 20 through pipe 21. It will be seen that the pressure of the heated and non-vaporized liquid in the separator 17 is controlled by a valve 0l placed in the pipe connection between the condenser and rundown tank. If no light fractions should be present in the liquid to be distilled, the heated liquid from still 14 may be conducted directly through pipe 16 and pipe 16 into chamber 1'7 by opening valve b and closing valves 'a and c.

The chamber or separator 17 has staggered overlapping baflles 22 and the vapors rising from the spray head encounter the same, whereby tarry and impure matters especially are retarded and allowed to fall back to the bottom of the chamber or separator 17. The remaining complex mixture escapes through pipe 23 into other parts of the system to be further treated.

In connection with the vapor line 23 I provide a series of partial condensers or towers, which are all of the same suitable construction, and description of one will suffice for all. The partial condenser, as shown in Fig. 2, includes a vertical shell 24, which has a transverse perforated plate or partition 25 near its lower end, the space below said plate constituting a receiving chamber 25. Above the center of the shell a transverse head 26 is mounted therein and receives the lower ends of the vertical tubes 27, which have their upperends terminating in a transverse head 2121 zlt a suitable distance below the top of the s e rl`he compartment between the heads 26 and 28 forms a tubular condenser for the.

Vapor passing upward within the tubes due to the cooling liquid on the outside of the tubes. This liquid may be fed by a pipe 29 entering just above the head 26 and its level maintained by outlet valves 30 placed at different elevations in the side of the shell between the heads. The level or height of the cooling liquid in the compartment may be definitely controlled by opening the valve at the desired elevation, thus providing mechanical means for regulating the temperature in the compartment corresponding to the final condensing temperature of the fraction or fractions it is desired to condense in this partial condenser. Similaimeans are provided in all the partial condensers serving to complete the condensation unit.

The compartment between the condenser and the plate 25 is filled with porous, cellular or baffle means '28 for retarding the upward flow of vapors passing through plate 25, whereby heavier parts of the fraction or fractions, it is desired to condense, are separated from the vapors, the balance or lighter parts of the fraction or fractions, it is desired to condense, are separated in tubes 27 forming the definite temperature controlled condenser. The total condensate formed in each partial condenser will fall back into the lower compartment,l below the plate 25. A gooseneck pipe 31 leads through the bottom of the shell forming a liquid seal and an extension of this pipe is connected with a cooling coil 32 below the condenser shell. When the liquid in the lower compartment 25 rises above the gooseneck seal it is constantly drained through pipe 3l into cooling coil 32 I 18 and pump 20 on and finally emitted bly vacuum trap 33, which is of substantially t e same construction as an ordinary steam vacuum trap. The liquid emitted from the trap falls into the storage tank 34 maintained at atmospheric pressure.

This process of separation and partial condensation in successive steps, makes it possible to continuously condense,'cool and emit fractions of hydrocarbon-liquid being distilled, the narrowness of each cut from each condenser being determined by the tempera- 'tures of the incoming and of the outgoing vapors. The cut from each condenser is cooled before being emitted into storage tank 34 to prevent oxidization. All cuts or products derived are Subj ect to continuous observation under' cooled atmospheric conditions, insuring uniform results from the operation of the process.

A series of two or more partial condensers are used in this process and a discharge pipe 35 leads from the top of one condenser to the receiving chamber of the succeeding condenser. Thus vapors not condensed in the first pass tothe second condenser and so on successively until all desired fractions are condensed. The vapors pass from the last partial condenser into a final. condensing worm 36 of suitable construction, wherein all remaining condensible vapors including steam, which may have been injected into the system, are condensed and conducted by gravity into vacuum separator 37. This separator has connection at its upper end with a vacuum pump 38 and at its lower end with a vacuum trap 39, for removal of water and condensate. A discharge of the separator, above the water level, to a storage tank 42 and includes vacuum trap 41 for removal of oil condensates.

It will be seen that between spray head one side, and vacuum pump 38 and vacuum tra-ps 41 and 39 on the other side, the entire process is effected under a vacuum. The vaporization, the separation of fractions desiredand final condensation is carried out continuously under a vacuum.

The degree of vacuum maintained is dependent on the temperature of the cooling water available for final step ofcondensation. of the mixed oil and water vapors through the worm 36, all fractions having lower boiling points than that of water at thev vacuum maintained in the worm 36 having been removed at atmospheric pressure. The mercury pressure constituting high vacuum cannot be definitely stated as it will vary according to the product being distilled and bythe temperature of the available cooling water in the final condenser, but as an eX- ai'nple it may be found that a vacuum not to exceed 50 m. 1n. mercury absolute pressure at any stage of the process Will be desirable undercertain conditions. In this process no pipe 40 leads out refrigerant is employed for condensation as the use of cooling water ordinarily available renders it possible to maintain a high vacuum to a practical degree, deriving all benefits in the finished products that are inherent Afrom low temperature at the point of vaporization Vof the liquid. Likewise the use of inert or noncondensible gas as carrier for the fractions to be recovered is undesirable in this process, as it would in effect destroy the high vacuum and increase the temperature at the point of vaporization of the liquid.

In using the process the hydrocarbon liquid is charged in a continuous fiow to the heat exchanger 12 through pipe 11 by pump 10 and passes out through pipe 13 into pipe still 14,` containing heating element or pipe coil 15. The hydrocarbon liquid is heated in the pipe still to the necessary degree and partly vaporized in separator 17, being ejected through spray head 18 at or above atmospheric pressure. Light fractions are separated, condensed and collected, the remaining heated liquid is conducted into chamber 17, where it is continuously ejected from spray head 18 and the remaining volatile ingredients vaporized under high vacuum. The chamber or separator 17 is maintained at a temperature permitting separation of tarry and impure matters. The va.- por or fine mist evolving from spray head 18 rises and pursues a circuitous path around' the baliies 22, the reflux falling to the bottom and the lighter vapors passing out through pipe 28 to the receiving chamber 25 at the bottom of the first partial condenser 24. The vacuum maintained in the chamber 17, this being the point of vaporization of the remaining volatile ingredients of the hydrocarbon liquid, is of practically the same degree as that maintained in the final condensing worin 36. The residue resulting from separation inlchaniber 17 passes out through pipe 19 and/into heat exchanger 12 and is permanently removed from the system by pump 2O through pipe 21. It is obvious that the heat in the residuum will be transferred to the charging stock passingthrough the heat exchanger. l

It is desirable, but not necessary, to inject superheated steam at various points of the .system as carrier and purifier of the vapors evolved during vacuum distillation, and fol` this purpose I have provided a supply pipe 43 with cut-offl valve 44 connected with the charging line -13 which includesa cut-ofi' valve 45. Betweenthe valves 44 and 45 a branch Ipipe 46 extends from pipe 43` and has a lateral extension 47 including a valve 47. This lateral extension supplies steam to the separator 17 when desired. An extension 48 for each partial condenser has connection with pipe 46 and' includes a valve 48. It will be seen that superheated steam may be supplied as desired to the various Vingliquid in said tubular condenser. refiux liquid resulting vations of condensation,

separating elements of the system and that it may be condensed in the final condensing worm 36 and separated out in vacuum separator 37 through vacuum trap 39, without causing water emulsions in the condensates of the heavier fractions.

The vapors passing into the first partial condenser will ascend through the'plate 25 into the compartment above where sufi'icient retardation is provided by the baiile means to separate the heavier parts of the fraction or fractions it is desired to condense. The ascending vapors now pass throufrh tubes 27 Where the lighter part of the fraction or fractions desired in the first step are condensed, and the total resulting reflux precipitated to the receiving chamber in the lower part of the shell. The tubes 27 between heads 26 and 28 form a condenser in which the temperature can be definitely controlled by varying the height of the cooling liquid supplied by pipe 29 and regulated by pipes 30. The down flowing refiux liquid covers the baille mea-ns in a thin film and the ascending hot vapors are brought into intimate conta-ct therewith, thereby aiding the separation by reabsorption of such light vapors which should have been carried to the next successive step of condensation. It will be seen that the temperature of the vapors passing into the vapor space above the tubular condenser is maintained at a definite degree, regulated by the height of the coclil- T ie from this step of par tial condensation and collected in receiving chamber, is cooled by coil 32 and emitted' through vacuum trap 33 into storage tank 34.

The uncondensed vapors which have passed through tubes 27 into vapor space above the tubularcondenser will flow through pipe 35 into the receiving chamber of the succeeding partial condenser, where the opercooling of reflux liquid, and discharge into storage tank are repeated.

I have connected a by-pass pipe 49 with pipe 23Vin advance of the .first partial condenser and provided a cut-off valve 49 there* in. The by-pass is connected to the condenser36, and has branches 50 with valves 51 connecting with pipe 35 at the lower inlet to each partial condenser. The bly-pass permits the omission of one or more of the partial condensers during the operation of the process, depending upon the nature of the liquid to be distilled.

AfterV the hydrocarbon liquid has been vaporized' and condensed into fractions. as may be desired, the final vapors are Kpassed through the condensing worm 36 and drawn into separator 37 from which the liquid is collectedy in tank 42.

An important factor in the operation of this process is that the vacuum at the point in the final condenser.

of vaporization 'is substantially the same as The boiling point of the complex mixture of the liquid is controlled by the vacuum at ization and not by the vacuum registered at the vacuum producing means. Undue friction, the'use of inert gas, or vaporization under insufficient circulation would tend to reduce the vacuum at the point of vaporiza- ,tion and consequently increase the temperature of the liquid to bey distilled, in some cases with disastrous results. Y

In the cooperative action of the initial residuum separation with the subsequent fractional condensation, the continuous and permanent removal of tarry and undesirable matters is quite essential, in order that the complex mixture may be purified before partial condensation takes place. In batch operated systems the impurities are not removed until distillation is completed and' due to the closenessof the fractions some impurities are carried over to the heavier cuts.

Under ordinary conditions all lubricating oil distillates contain light fractions that niust be removed by separate skimming process before the charging stock is in condition to be distilled under high vacuum andgive results commensurate with the cost of vacuum distillation in highly specialized equipment. Theuse of superheatcd steam in the various steps of this process is dependent upon tlie character of liquid to be distilled, but may be omitted when the character of such liquid does not require its use. The formation of water `emulsions in the heavier fractions during vacuum distillation is prevented by the high temperature maintained in each partial condenser, which, prior to the final condensation, is always above the boiling point of water.

The process may be employed in the rerunning or re-refining of any hydrocarbon or kindred liquid.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is l. The continuous process of distilling and separating desirable lubricating oil fractions of different boiling points from a hydrocarbon mixture containing the` saine which comprises primarily heating a continuous fiow of the mixture without vaporization of the desirable lubricating oil fractions to a temperature sufficient for vaporization of said fractions under vacuum ina subsequent step of the process, first removing from the liquid at atmospheric pressure such lighter fractions of the mixture as will be vaporized at atmospheric pressure, continuously distilling the remaining liquid without additional heating and under sufficiently high uniform vacuum to effect vaporization of the desirable lubricating oil fractions, and fractionally conthe point of vapor-j j to a temperature sufcient to vaporize said A densing the resulting vapors according to their boiling points.

2. The continuous process of distilling and separating desirable lubricating oil fractions of different boiling points from a hydrocarbon mixture containing the same which comprisescontinuously passing a confined stream of the mixture through a heating zone, heating the stream in said zone Without vaporization of the desirable lubricating oil fractions fractions under vacuum in a subsequent step of the process, discharging said stream into an enlarged chamber maintained at atmospheric pressure thereby distilling lighter fractions of the mixture, removing and condensing. said lighter fractions, introducing the remaining mixture of unvaporized fractions while still in heated condition and without furtherheating into a second enlarged chamber lmaintained under sufficiently high uniform vacuum to effect vaporization of the desirable lubricating oil fractions, and fractionally condensing the resultant vapors according to their boiling points.

3. The continuous process of distilling and separating desirable lubricating oil fractions of different boiling points from a hydrocarbon mixture containing the same which comprises primarily heating a continuous fiow of the mixture Without vaporization of the desirable lubricating oil fractions to a temperature sufficient for vaporization of said fractions under vacuum in a subsequent step of the process, first removing from the liquid at latmospheric pressure such lighter fractions of the mixture as will be vaporized at atmospheric pressure, then continuously distilling the remaining liquid without additional heating and under sufiiciently high uniform vacuum to effect vaporization of the desirable lubricating oil fractions, fractionally condensing the resultant vapors under constant vacuum of substantially the same degree as maintained in the distillation of said lubrieating oil fractions.

4. The continuous process of distilling and separating desirable lubricating pil fractions having different boiling points from a hydrocarbon mixture containing the same which comprises primarily heating a continuous fiow of the mixture without vaporization of the desirable lubricating oilvfractions to a temperature at which said fractions will be vaporized when maintained under high vacuum, first distilling from the mixture at atmospheric pressure such lighter fractions as will vaporize at atmospheric pressure, then oontinuously Vaporizing under suflicientlv high uniform vacuum and without additional heating all of the desirable unvaporized lubricating oil fractions, removing the unvaporized portion of the mixture from the system, and fractionallv condensing the .resultant vapors according to their bolling points under constant vacuum 'of substantially the same degree as maintained in the distillation of said lubricating oil fractions.

5. The method of distilling petroleum which comprises first subjecting petroleum to distillation at substantially atmospheric pressure to produce distillate oils and a res1dual oil by heating it ina pipe coil to a temperature sufficient to vaporize considerable proportions of the oil contained in the petroleum,discharging the resulting product into a vapor separating chamber at approximately atmospheric pressure, separately collecting and condensing the oil vapors thus produced and. withdrawing the residual oil continuously while it is still at approximately the temperature of the first distillation and immediately subjecting it to a high vacuum to effect further distillation of high boiling point oils therefrom by the self-contained heat of the'hot residual oil.

6. That improvement in methods of distilling petroleum, which comprises first producino' distillate oils and a residue containing lubricating oils, by heating the petroleum while fiowing in a restricted stream of small cross-sectional area in a continuous manner without objectionable decomposition, discharging the heated petroleum into an expansion zone maintained at substantially atmospheric pressure, with sudden volatilization of a portion of the normal oil content of the petroleum, cooling the vapors to condense distillate oils, withdrawing the residue containing desirable lubricating oils and thereafter subjecting said residue to a single high vacuum While utilizing only the self contained heat of the residual oil, to evolve a complex vaporized mixture containing the desirable lubricating oils and separately condensing the evolved vapors according to their boiling points.

7. That improvement in methods of distilling petroleum which comprises first producing distillate oils and a residue containing lubricating oils by heating the petroleum While flowing in a restricted stream of small cross-sectional area in a continuous manner withoutI any substantial objectionable decomposition, discharging the heated petroleum into an expansion zone maintained at approximately atmospheric pressure, with resultant volatilization of a portion of the normal volatile content of the petroleum, cooling the vapors so produced to condense distillate oils, withdrawing the residue containing lubricating oils from the atmospheric expansion zone, and thereafter subjecting said residue to an unheated high vacuum tillate light oils and a residual oil, said lat-- ter named oil containing a substantial proportion of the desirable lubricating oils, withdrawing` the residual oil so produced and continuously feeding it into an unheated zone maintained under vacuum. whereby the self contained heat of the residue and the vacuum cause to be vapor-ized the desirable lubricating oil fractions contained in the residue, and condensing the lubricating oil fractions so vaporized.

9. The method of continuously distilling liquid hydrocarbons containing aC plurality of products having different boiling points, which comprises passing` the liquid hydrocarbon through a restricted stream of small cross sectional area and heating it therein to a temperature sufficient tovvanorize considerableproportions of the products contained in the liquid hydrocarbon, subjecting the heated hydrocarbon to atmospheric pressure to effect complete vaporization of the said considerable proportions of products, separately collecting and condensing the said products. withdrawing the residual hvdrocarbon liquid. and subjecting the heated residue to a high vacuum, in an unheated zone, while it is at a sufiicientlv high temperature to effect vaporization therefrom of additional products having higher boiling points, removing the unvaporized residual portionof the hydrocarbon liquid andthereaft-er separately collecting and condensing the products evolved by the'vaporization under vacuum.

10. The process of continuously producing a plurality of lubricating oils of different grades from petroleum containing the same, which comprises flowing the petroleum through a zone mantained at approximately atmospheric pressure. said petroleum being in a heated condition, whereby the lower boiling point oils contained in the petroleum are vaporized, removing the vaporized oils from the petroleum, flowing the petroleum into an unheated zone maintained under a high vacuum, said petroleum being at a high temperature when admitted to the vacuum zone, whereby the action of the vacuum on the hot petroleum evolves a complex distillate containing the desirable lubricating oil fractions, carrying off from the vacuum zone as a residue the heavy, tarry, unvapori'zed portions of the petroleum, separating the complex distillate from the residue, and fractionally condensing the complex distillate, according to the boiling points of the oils which it contains, under a constant vacuum of substantially the same degree as employed in effecting the distillation under vacuum.

11.l That improvement in methods of extracting oils of intermediate boiling points from a complex hydrocarbon mixture containing the salne, which comprises subjecting a heated and continuously fiowing stream of the mixture to the following steps in the sequence named: First, removing at substantially atmospheric pressure the lower boiling point oils contained in the continuously flowing mixture; second, placing under a single `high vacuum in the absence of additional heat, the continuously flowing miXture-from which the lower boiling point oils have been removed to effect complete and simultaneous vaporization of the intermediate boiling point oils; third, eliminating from the continuously flowing mixture those heavyV and impure matters not vaporized under vacuum; and, fourth, fractionally condensing the vaporized oils according to their boiling points.

12. That improvement in methods of extracting oils of intermediate boiling points from a complex hydrocarbon mixture containing the same, which comprises subjecting a heated and continuously flowing stream of the mixture to the following steps in the sequence named: First, removing at substantially atmospheric pressure the lower boiling point oils contained in the continuously flowing mixture; second, placing the continuously flowing mixture, from which the lower boiling point oils have been removed, under a high vacuum in the absence of additional heat, to effect, in a. single distillation stage vaporization of a complexmixture of the intermediate boiling point oils; third, A eliminating from the continuously flowing mixture those heavy and impure matters not vaporized under vacuum; fourth, fractionally condensing the complex vaporized mixture to produce oils of different boiling points.

In testimony whereof I affix my signature.

WARREN W. GRIMM. 

